1. Field of the Invention
The present invention relates to a method of fabricating an optical interference color display, and more particularly to a method of fabricating an optical interference color display capable of controlling air gaps formed in the optical interference color display precisely.
2. Description of the Related Art
Panel displays, such as liquid crystal (LCD) displays, organic electro-luminescence (OEL) displays, or plasma display panels (PDPs), which are light and slim, have been widely used in our daily life. Wherein, LCD displays have gradually dominated the market. However, LCD displays still have some disadvantages. For example, the angles are not wide enough, the response time is not fast, and requirement of using polarizer results in poor utilization of light source.
An optical interference color display has been developed to date. FIG. 1 is a schematic drawing showing a conventional optical interference color display. The conventional optical interference color display 100 comprises a transparent substrate 110, a first electrode structure 120, a patterned support layer 130 and a second electrode layer 140. The first electrode structure 120 comprises a plurality of first electrodes 122, an absorption layer 124 and an optical layer 126, from bottom to top. Note that a plurality of air gaps G1-G3 is formed (defined) between the first electrode structure 120 and the optical layer 126.
After propagating into the first electrode structure 120 through the transparent substrate 110, light propagates to the first electrode structure 120 through the air gaps G1-G3. Then, the light is reflected by the second electrode layer 140 and propagates through the first electrode structure 120. Due to different light interferences in the different air gaps G1-G3, different color lights, such as red, green and blue lights, are generated for displaying. The forming of the air gaps G1-G3, however, is determined by the thicknesses of the sacrificial layers. Detailed description will be mentioned later. In other words, the quality of the sacrificial layers will affect the optical performance of the optical interference color display 100.
FIGS. 2A-2D are cross sectional views showing progress of a method of forming sacrificial layers. Referring to FIG. 2A, a transparent substrate 110 is provided. A first electrode structure 120 is then formed over the transparent substrate 110. The first electrode structure 120 comprises a plurality of first electrodes 122, an absorption layer 124 and an optical layer 126, from bottom to top. In addition, a first area 10, a second area 20 and a third area 30 are defined on the first electrode structure 120.
Referring to FIG. 2B, a first sacrificial layer 132, e.g., amorphous silicon, is entirely deposited. A photolithographic process and an etch process are performed to remove the first sacrificial layer 132 outside the first area 10, the second area 20 and the third area 30 to form a first sacrificial layer 132 with designated patterning.
Referring to FIG. 2C, a second sacrificial layer 134 is entirely deposited. The second sacrificial layer 134 and the first sacrificial layer 132 are the same material. A photolithographic process and an etch process are performed to remove the second sacrificial layer 134 outside the second area 20 and the third area 30 to form a second sacrificial layer 134 with designated patterning. Note that while removing the second sacrificial layer 134 of the first area 10 by the etch process, the first sacrificial layer 132 and the second sacrificial layer 134 are the same material, i.e., the same etching rate. Accordingly, the first sacrificial layer 132 is easily damaged by the etchant used in the etch process such that the original thickness of the sacrificial layer 132 is changed. That causes impact to the subsequent processes.
Referring to FIG. 2D, a third sacrificial layer 136 is entirely deposited. The third sacrificial layer 136, the second sacrificial layer 134 and the first sacrificial layer 132 are the same material. A photolithographic process and an etch process are performed to remove the third sacrificial layer 136 outside the third area 30 to form a third sacrificial layer 136 with designated patterning. The process of forming the sacrificial layers is thus complete. Note that the third sacrificial layer 136 is on the first sacrificial layer 132 while the third sacrificial layer 136 of the first area 10 is removed by the etch process, thus the first sacrificial layer 132 is damaged easily. Similarly, while removing the third sacrificial layer 136 of the second area 20, the third sacrificial layer 136 is on the first sacrificial layer 132, and the first sacrificial layer 132 and the third sacrificial layer 136 have the same etching rate. Accordingly, while the third sacrificial layer 136 is removed, the second sacrificial layer 134 is also damaged easily.
Finally, a photoresist layer is entirely coated. The photoresist layer is then patterned to form a patterned support layer 130. Then, a second electrode layer 140 is formed over the sacrificial layers with different thicknesses of the first area 10, the second area 20 and the third area 30, and a portion of the patterned support layer 130. Thereafter, etchant, such as XeF6, is then used to remove all sacrificial layers 132, 134 and 136 to form different air gaps G1-G3 as shown in FIG. 1.
In other words, the thicknesses of the deposited sacrificial layers determine the formation of the air gaps G1-G3. If the desired thicknesses of the sacrificial layers are changed due to the damaged sacrificial layers, the dimensions of the air gaps G1-G3 cannot be precisely controlled. The optical performance of the optical interference color display 100 is seriously affected. Under the described unstable manufacturing processes, yields are declined and manufacturing costs are also increased.